1. Field of the Invention
The present invention relates generally to semiconductor fabrication methods and, more particularly, to a system for fabricating contact holes.
2. Description of Related Art
Integrated circuit devices typically are composed of layers of semiconductor and insulating material modified using known manufacturing methods to form active and other microstructures such as gates, drains, sources and the like. These microstructures then are interconnected with conducting material in order to provide the desired functionalities of a given integrated circuit. The interconnecting may be achieved using contact holes filled with a highly conductive metal. Known manufacturing methods have been devised to achieve the required interconnections.
Conducting metal in a contact hole must be isolated from the surrounding integrated circuit material. Failure to isolate properly the conducting metal from those surrounding materials may result in intermixing of the conducting metal and the other materials or their functionalities due to, for example, diffusion in one direction and/or the other. These undesired diffusion processes tend to degrade performance of the integrated circuit and to result in lower yields. In order to provide proper isolation between the different classes of material, a thin layer of barrier material is often disposed between the conducting metal and the surrounding material, e.g., by way of lining the contact hole with barrier material as a step in the fabrication process.
Creating a conducting path through a contact hole in the integrated circuit material can involve at least two steps, one being to deposit a thin film of barrier material that lines the contact hole and the other being to fill the lined contact hole with conducting material.
As contact hole sizes become smaller, slight variations in the process of depositing the film of barrier material can become more important. For example, an overhang profile may result that may partially occlude an opening to a contact hole, thereby impeding metal fill-in of the contact hole and producing imperfections such as voids and/or seams in the conducting metal fill-in. These imperfections can degrade reliability, reduce yields, and increase manufacturing costs of the integrated circuits.
A need thus exists in the prior art for a method of eliminating barrier material overhang that can result in incomplete fill-in of contact holes in an integrated circuit. A further need exists for apparatus to implement the method in fashions which are reliable yet rapid.